The present invention relates to seats for use in aircraft, such as, helicopters. More specifically, but without limitation, the present invention relates to a crashworthy seat that repositions the occupant prior to and/or during a crash event to increase the survivability of the occupant and decrease the harmful effects of a crash.
There have been many attempts to improve occupant survivability in a crash, especially with regard to helicopters. Such efforts have recently been directed to the occupant seat assembly including the seat frame, seat base and related parts. These crashworthy seat assemblies have been developed to stroke (i.e. to move usually in a downward direction relative to the aircraft floor) upon severe impact and usually activate energy absorbing devices thereby absorbing all or a portion of the crash energy transmitted to the seat. These seat assemblies may also be designed to plastically deform upon impact thereby absorbing an additional amount of the crash energy. As a result, the forces and accelerations experienced by an occupant in a crash are reduced and frequently minimize or eliminate injuries and save lives.
However, the amount of energy that can be absorbed is limited by the efficiency of the energy absorbing devices, the total distance available for the seat to stroke, and the energy absorbing capabilities of the plastically deformed seat assembly. In addition, it has been determined that a stroking seat sometimes causes the control stick of a helicopter to be impaled into the body or head of the pilot causing additional injuries.
Another problem associated with current seats is the positioning of the occupant. Most seats position the occupant in a substantially upright position prior to a crash. During a crash event, the seat remains substantially upright even in cases where the seat strokes or otherwise moves to absorb impact. As a result, an occupant""s spine can be placed in severe compression from the force of the crash; the occupant""s head and body are vulnerable to impacting the control stick or other object; the seat shoulder straps are subject to large forces which tend to stretch the strap material; the occupant is subject to submarining, that is, being forced under and out of the seat belt due to the force of the crash; and the occupant""s internal organs are subjected to compressive forces due to, for example, compression of the abdomen.
There is thus a critical need in the art to provide an improved seat assembly that exhibits the benefits and advantages of existing designs and also provides additional protection during a crash event.
There is also a critical need to provide an improved seat assembly that exhibits the benefits and advantages of existing designs yet will prevent the control stick of a helicopter, for example, from contacting or being impaled into the body or head of the occupant.
There is a further critical need to provide an improved seat assembly that will place an occupant in a position that will reduce injury to internal organs and increase the magnitude of the crash event that an occupant can survive.
There is a critical need to provide an improved seat assembly that will reduce the undesirable effects of submarining and decrease the forces applied to the restraining belts.
There is another critical need to provide an improved seat assembly that can provide the improvements and benefits of the present invention while minimally impacting existing seat components, such as, restraint systems, inertia reels and armor plates.
Accordingly, the preferred embodiment of the present invention includes a seat for supporting an occupant, first and second energy absorbers for absorbing at least a part of the impact of a crash and a pivot for repositioning the seat to a more desirable attitude. In operation, the energy absorbing devices react to the force of a crash event when the force exceeds a predetermined value to allow or cause the seat to be repositioned to a more desirable attitude. Other embodiments of the present invention are included.